As a train runs along a set of rails, it applies lateral forces to the rails, pushing them outward at the point where they are fastened to the supporting ties. It is obviously desirable to minimize the effect of these lateral forces, as any excessive movement of the rail will move the rails heads apart, widening the gauge of the track and allowing the train wheels to slip off the inside of the rail, causing a derailment. Of equal concern is the longitudinal force applied to the rail as the train runs along the rails and due to temperature changes. This force tends to push or pull the rail, and the rail plate holding it to the rail, off the edge of the tie, leaving that portion of the rail unsupported and weak, or disrupting the rail anchoring to the tie to resist thermal longitudinal force, again leading to the possibility of a derailment.
It is known to minimize the effects of the train's forces by securing the rails and ties against movement. For example, U.S. Pat. No. 9,758,932 to Lu et al. describes a ballastless track system wherein concrete slabs carrying the rails are provided with a depending structure on its underside that interacts with the underlying base to try to restrain movement of the entire slab and the overlying rails. However, such systems do not restrict the movement of the rails themselves, apart from the entire assembly as a whole. This may be less efficient and effective.
More typically, movement of a rail supported on a tie is directly restricted by holding it down on a rail plate, which usually includes a rail seat to accommodate the base of the rail. The rail or rail plate is in turn secured to the tie by fasteners. The fasteners are generally exposed on the tie, which can simplify the inspection, repair and/or replacement of the fasteners as needed. However, in a derailment, these fasteners are vulnerable to damage when one or more train wheels forcefully impacts the area beside the rail. This can significantly delay repair after a derailment, and the return of the rail to full availability. Simply covering the fasteners can make it very difficult to inspect the assembly throughout its lifetime, in order to confirm that it properly secures the rail or rail plate. If the assembly is not secured or loosens over time, a catastrophic separation of the rail from the tie may occur.
U.S. Pat. No. 2,276,799 to Spencer and U.S. Pat. No. 715,698 to Saleme both provide ties having shaped keyways in their upper surfaces, in order to interlock with components passing over the tie. Saleme discloses a longitudinal passageway through which a rail base is fed. Spencer discloses a lateral passageway, either in a rail plate or in the tie surface, into which a projection on the underside of the rail is fitted and slides horizontally to interlock with the tie or rail plate. The configuration of the rail and the keyed surface are both relatively complex and would not seem to provide the expected lateral support to a rail.
GB Patent No. 1169715 to Waters discloses a rail for which additional lateral support is provided by using a rail with a depending rib that is located in a linear recess extending across the tie, with a resilient pad between the rail and the tie. In another embodiment, Waters provides a standard rail, and a resilient pad having a depending rib that fits into the recess. However, the first embodiment is likely susceptible to abrasion and deterioration between the rail base and the tie, as there is no plate between them. In the second embodiment, having the resilient pad seems to provide less additional lateral support to the rail than would a stiffer or stronger piece, such as the rail base or a rail plate.
U.S. Pat. No. 2,242,773 to Boyce discloses a tie plate with a pair of ribs on an under surface that are embedded in a tie. These are located towards the outer edge of the plate, just outside the rail base. U.S. Pat. No. 4,108,378 to Raymond discloses a rail plate having depending ribs, and a tie having a recess with grooves running across the width of the tie. The rail plate fits into the recess while its depending ribs fit into the grooves, thereby anchoring the plate to the tie and preventing lateral movement. Connection of the tie plate to the tie is provided by wood screws, while spikes secure the rail to the plate. In both of these patents, the depending rib provides additional lateral support to the plate, preventing it from moving sideways on the tie when a train passes. However, the linear shape and straight orientation of the ribs and grooves relative to the tie does not do anything to restrict longitudinal movement of the rail plate on the tie.
U.S. Pat. No. 3,957,201 to Johnson shows a concrete tie having an anchor structure set into a recess and a rail seat formed by base plate. A rail plate pad is located between the anchor and the rail. A threaded stud is attached to the underside of plate, preferably by spot welding, presumably to anchor the anchor structure into the body of the concrete tie. The threaded stud is permanently attached (welding being the preferred method) and evidently intended to be completely embedded and not accessible for repairs or replacement.
U.S. Pat. No. 4,925,094 to Buekett similarly discloses a concrete tie with a cast-in rail plate defining a rail seat, with downwardly projecting lugs embedded in the tie body. The lugs are provided to ensure a mechanical connection between the plate and the tie. Again, due to the nature of the tie and the connection with the lugs, removal of the rail plate for replacement or repair is not feasible.
U.S. Pat. No. 8,625,878 to Haas et al. describes an inspection system for a railway track that uses vision technology to read and compare a configuration of rail components with safety requirements stored in an associated processor. Similarly, U.S. Pat. No. 9,441,956 to Kainer et al. discloses a tie inspection system that uses a generated light to produce an image of the tie in order to compare it with stored parameters. U.S. Pub. No. 2012/0192756 to Miller et al. discloses a vision-based inspection system mounted on a railcar or other vehicle. However, all of these systems are relatively complex and require computer processing resources, along with the associated time and cost limitations. A visual inspection to ensure that the rail components are in place is a simpler and less expensive alternative.
It is therefore an object of this invention to provide a tie and a rail fastening assembly that overcomes the foregoing deficiencies.
It is a further object of the invention to provide a fastening system that does not require traditional insulators between the rail and clip, yet still provides rail-to-rail electrical isolation.
It is further an object of the invention to provide a system wherein lateral and longitudinal forces of passing trains are transmitted from the rail into the tie, not into the plate-to-tie fastening system. Although concrete ties historically do not use rail plates between the rail and the tie, the use of a plate will significantly reduce or even eliminate rail seat deterioration as it reduces the stresses that pass from the rail base into the concrete. Using a rail plate significantly increases the contact area (plate to concrete tie) as compared to the contact area of a rail base directly on the concrete tie, thus helping to spread the forces from the rail plate over a larger area of the tie and therefore reducing or eliminating abrasion of the concrete.
It is a further object of the invention to provide a system in which alternate fastening systems may be employed simply by changing the rail plate, rather than the tie.
It is a further object of the invention to provide a plate-to-tie fastening system that requires only a minor amount of clamping or connecting force; however, if a fastener is used, a single fastener may be all that is required to provide the needed force to retain the tie plate on the tie. Additional means may be used to prevent loosening of the fastener.
It is a further object of the invention to provide a fastening system located to protect it from damage, for example during a derailment.
It is a further object of the invention to provide a rail plate and rail pad that facilitate inspection of the assembly in place on a tie, when used together.
It is yet a further object of the invention to provide a mechanism to allow easy verification of whether the fastening system is properly retaining the plate and rail on the tie.
These and other objects of the invention will be better understood by reference to the detailed description of the preferred embodiment which follows. Note that the objects referred to above are statements of what motivated the invention rather than promises. Not all of the objects are necessarily met by all embodiments of the invention described below or by the invention defined by each of the claims.